claim pieces from list of available pieces

core/src/main/groovy/com/muwire/core/download/Pieces.groovy

@@ -38,6 +38,18 @@ class Pieces {
         }
     }
     
+    synchronized int claim(Set<Integer> available) {
+        for (int i = claimed.nextSetBit(0); i >= 0; i = claimed.nextSetBit(i+1))
+            available.remove(i)
+        if (available.isEmpty())
+            return -1
+        List<Integer> toList = available.toList()
+        Collections.shuffle(toList)
+        int rv = toList[0]
+        claimed.set(rv)
+        rv
+    }
+    
     synchronized def getDownloaded() {
         def rv = []
         for (int i = done.nextSetBit(0); i >= 0; i = done.nextSetBit(i+1)) {

core/src/test/groovy/com/muwire/core/download/PiecesTest.groovy

@@ -34,4 +34,19 @@ class PiecesTest {
         pieces.markDownloaded(piece2)
         assert pieces.isComplete()
     }
+    
+    @Test
+    public void testClaimAvailable() {
+        pieces = new Pieces(2)
+        int claimed = pieces.claim([0].toSet())
+        assert claimed == 0
+        assert -1 == pieces.claim([0].toSet())
+    }
+    
+    @Test
+    public void testClaimNoneAvailable() {
+        pieces = new Pieces(20)
+        int claimed = pieces.claim()
+        assert -1 == pieces.claim([claimed].toSet())
+    }
 }